The present invention relates to keyboards for use in computer terminals, typewriters, and the like, and more particularly to a mechanism for maintaining an oddly-shaped keytop level during its downward and upward travel when used on a keyboard.
Various types of keyboards are used on typewriters, computer terminals and the like for typing or entering data into a computer. Such keyboards are typically manufactured from a plurality of separate keyswitches which are lined up on a circuit board. Each individual keyswitch has a keytop thereon which is generally stamped or otherwise marked with the number or letter which that keyswitch represents. Thus, a keyboard for a conventional typewriter will have something on the order of 50 separate keyswitches, 26 of them representing the letters of the alphabet, 10 representing the digits 0-9, with additional switches for various punctuation and machine functions.
Most keytops used in conventional keyboards are square or rectangular in shape. However, for some machine functions, keytops of different shapes are used. One shape which is often used for certain keyboard functions is an L-shaped keytop. Such keytops provide a convenient way of increasing the useable keytop area by providing an extension into an adjacent row of the keyboard without upsetting the esthetics of the keyboard. Typically, one portion of the L-shaped keytop is used while typing on the main or "alpha" portion of the keyboard while the other portion of the keytop (usually the "ascender" portion of an L-shaped keytop) is used while making entries on an auxiliary group of keyswitches located beside the main keyboard array. It is therefore important that an oddly-shaped keytop, such as an L-shaped keytop, be capable of use by pressing any part thereof. This feature is known as "full top surface utilization".
Full top surface utilization of oddly-shaped keytops is often difficult to provide, e.g., when used in conjunction with low profile keyswitches, when the keyswitch itself does not provide sufficient support for the entire keytop.
In the past, attempts to provide full top surface utilization of L-shaped keytops have not been entirely adequate. The objective of any solution is to prevent the keyswitch from binding when pressing the keytop at a point which is not directly over the keyswitch. One prior solution has been to limit the useable area of the keytop so that the forces created by a keyboard user pressing upon the keytop are directed to an area compatible with the action of the keyswitch. A disadvantage of this solution, however, is that the limited area defeats the purpose of the specially shaped keytop, i.e., the provision of additional keytop area. Another solution has been to incorporate a lever stabilizer mechanism similar to those used for multi-wide keytops such as space bars. However, due to the limited widths that can be obtained in oddly shaped keytops, for example in the narrow ascender portion of an L-shaped keytop, such lever stabilizer mechanisms are not adequate.
It would be advantageous to provide full top surface utilization of an oddly shaped keytop, such as an L-shaped keytop, along with smooth, level keyswitch actuation. Such features should be available even when only a narrow keytop section, such as a narrow ascender portion of an L-shaped keytop, is to be maintained level. Such a levelling mechanism should be economical, easy to manufacture, and capable of being fabricated from a minimal number of parts. This invention relates to such a keytop levelling mechanism.